The floppy disk drive typically operates at low rotational speeds and utilizes a recording medium that is removable and interchangeable with other similar devices. The floppy disk is less expensive and more rugged than the hard disk. However, the floppy disk has severe limitations with regard to possible data densities. The floppy disk is composed of a plastic substrate, such as Mylar or polyethylene terephthalate, that is coated with a slurry of magnetic particles. This coating cannot support the high areal densities of magnetic recording possible with the thin sputter deposited films of the hard disk. And the plastic substrate of the floppy disk cannot survive the high temperatures required by the sputter deposition used for the hard disk. Also, the plastic substrate of the floppy disk exhibits anisotropic properties which further limit the storage densities possible. Other techniques, such as vapor deposition and low temperature sputtering, have been used with the plastic substrate. However, the magnetic characteristics obtained do not approach those of the hard disk.
Disk drive data storage devices are becoming more portable and mobile with increased emphasis on storage capacity, speed of data transfer, shock resistance, and reduced power consumption. With motivation toward these goals, White, J., 2005, “Slider Air Bearing Design Enhancements for High Speed Flexible Disk Recording,” ASME Journal of Tribology, 127, pp. 522-529 described the performance of an asymmetric longitudinally slotted rail opposed magnetic head slider arrangement for use with a high speed flexible Mylar disk. The complete disclosure of this reference is herein incorporated by reference. In that work, the disk thickness was 63.5 μm (0.0025 in), and the slider was of the industry standard nano configuration (2.00 mm×1.60 mm footprint). The static flexibility of the disk was utilized to shape and deflect the disk at the sub-micron level over the slider air bearing surface (ABS). This allows the minimum fly height to be focused on the recording element (RE), with higher fly heights elsewhere, tending to minimize contact between slider and disk. This slider and disk arrangement also provides for improved slider/disk response to mechanical shock by using the disk static flexibility to position the thin and stiff air film at the RE opposite a much thicker and less stiff air film on the other side of the disk.
A storage medium alternative that combines some of the best features of both the hard disk and the floppy disk is the metal foil disk described by Nigam, A., and White, J. W., 1999, “Metal Foil Disk for High Areal Density Recording in Environments of High Mechanical Shock,” U.S. Pat. No. 5,968,627, incorporated herein by reference. This disk makes use of a thin metal substrate with isotropic properties together with recording layers typical of a hard disk. It requires less operational energy than a hard disk while providing storage densities and data transfer rates typical of the hard disk. In addition, the metal foil disk, due to its flexibility, offers increased mechanical shock resistance as compared to a hard disk. And manufacturing cost of the metal foil disk promises to be less than that of the hard disk due to decreased material cost and process advantages. (See Nigam, A., and White, J. W., 1999, “Metal Foil Disk for High Areal Density Recording in Environments of High Mechanical Shock,” U.S. Pat. No. 5,968,627 and Washburn, H., 2000, “Systems and Methods for Making a Magnetic Recording Medium on a Flexible Metal Substrate,” U.S. Pat. No. 6,113,753, incorporated herein by reference).